Recently, the demand for an original reading apparatus as an image processing apparatus is increasing. Examples of the original reading apparatus are a flat bed type original reading apparatus having an original plate and a film reading apparatus. Another example is an image processing apparatus capable of reading an image by replacing an interchangeable printhead of a printer with a scanner head having substantially the same shape as the printhead.
FIG. 2 is a view showing the construction of an image processing apparatus according to a preferred embodiment of the present invention. FIGS. 3A and 3B are views showing the outer appearance of a scanner head which can be attached to the image processing apparatus shown in FIG. 2. One conventional problem will be explained below with reference to FIGS. 2, 3A, and 3B. A detachable printhead 1 or a detachable scanner head 300 is selectively mounted on a carrier 2 of the image processing apparatus. The scanner head 300 has a scanner head case 300b which is substantially cubic. In the internal hollow portion of this scanner head case 300b, a sensor 302, a field lens 304, an image forming lens 301, illuminating LEDs 306, and the like as image reading parts are arranged. This scanner head 300 is mounted on the carrier 2 while being guided by guide portions 314. The scanner head 300 is electrically connected to the main body (image processing apparatus) by bringing a carrier terminal portion (not shown) into tight contact with a head terminal portion (terminal board) 309. This head terminal portion 309 is connected to a main electric circuit board for controlling the sensor 302 and the illuminating LEDs 306 in the scanner head case 300b via a printed circuit board 305.
To improve the ease of assembly of the internal parts of the scanner head 300, it is preferable to form as large an assembly opening as possible in the scanner head case 300b. However, a large assembly opening lowers the strength of the scanner head case 300b. In particular, a large load acts on the head terminal portion 309 for receiving electrical signals from the main body (image processing apparatus), in order to obtain a sufficient contact with the carrier terminal portion. Since this deforms the scanner head case 300b, it is impossible to obtain a sufficient contact as an original purpose.
FIG. 8 is a view showing the optical configuration of a general scanner unit. Another conventional problem will be described below with reference to FIG. 8. Light emitted from a light source 86 irradiates an original 18 via a condenser lens 85. The reflected light from the original 18 forms an image on a sensor 84 through lenses 82 and 83, and the sensor 84 reads this image. The focus can be placed on the sensor 84 by moving the lens 83 in the direction of an arrow a along an optical axis 81. In addition, any ramp of the read image can be eliminated by pivoting the sensor 84 through an angle θ on the optical axis 81.
These two adjustments are carried out when the sensor unit is almost completely assembled, because it is preferable to carry out these adjustments while monitoring outputs from the sensor. However, the focus adjustment of the above two adjustments is sometimes impossible to perform after assembly, if dimensional variations of the components or focal length variations of the lenses are large. When this is the case, it is necessary to disassemble the sensor unit, adjust a distance b in FIG. 8, reassemble the unit, and readjust the lens 83 in the direction of the arrow a, resulting in a very troublesome operation.
Still another problem of this conventional image processing apparatus is as follows. The head terminal portion 309 is attached to the outside of the scanner head case 300b and connected to the main electric circuit board for controlling the sensor 302 and the illuminating LEDs 306 in the scanner head case 300b via the printed circuit board 305. When a mounting positional error of the scanner head 300 is taken into consideration, it is necessary to give a considerable size to each contact of the head terminal portion 309 and form adequate intervals between these contacts. This increases the width of the head terminal portion 309 to some extent. On the other hand, the width of the printed circuit board 305 is preferably small in order to reduce the influence of noise and external pressure. Therefore, a slit hole is formed in one wall surface of the scanner head case 300b, and the head terminal portion 309 is extracted to the outside of the scanner head case 300b through this slit hole. In this case, however, the extraction hole remains in the wall surface, and light enters through this hole. To solve this problem, the conventional approach is to seal up the extraction hole with a tape or the like, and this is a very tedious operation.